1. Field of the Invention
The present invention relates to an image display device including light emitting elements such as LEDs arranged in a plane and a display unit used therefore.
2. Description of the Related Art
A large image display device in a related art includes many display units containing light emitting elements arranged in a plane. Recently, LEDs (light emitting diodes) have become main stream of light emitting elements because the layout and arrangement pitch of LEDs of three primary colors can be arbitrarily designed. Accordingly, large image display devices having various resolution and brightness can be formed depending on the intended use.
The display units of the large image display device include pixels or picture elements containing subpixels of the respective colors of at least R (red), G (green), B (blue) arranged in a square lattice for display of full-color video (in the following description, the term “subpixel” is used to mean the same thing as an individual light emitting element).
Further, R, G, B are assigned to three pixels of four (2×2) pixels, and an appropriate color is assigned to the remaining fourth pixel depending on the intended use. For example, G has been assigned to the fourth pixel in a large image display device in which CRTs or discharge tubes are arranged, and R has been assigned thereto in a device in which LEDs are arranged (see Japanese Patent No. 3702699). Lately, there is an example that W (white) is assigned as a pixel configuration of an organic EL or the like, for example (see Japanese Patent No. 3416570).
Especially, recently, an LED device called 3-in-1 having LED chips of three colors of R, G, B in one LED lamp have been emerged. When such 3-in-1 type LED devices are arranged, one pixel emits three primary colors, and the three colors become easier to be mixed than in the system in which three LEDs of R, G, B are arranged. Accordingly, the visual distance at which a viewer watches an image becomes shorter. As the 3-in-1 type LED device arrangement, there is a system as disclosed in JP-A-2001-75508.
In this type of large image display device, it is necessary to arrange pixels in higher density with a smaller pixel pitch as the resolution becomes higher. Accordingly, in a high resolution large image display device including arranged LEDs, for example, the number of LEDs per unit area increases and the cost becomes higher. Especially, in the use of high-quality image display with high-definition contents like “Hi-Vision”, there is a problem that the arrangement density of LEDs becomes higher and the cost dramatically increases.